Reference point
Smell a dry, unused bar of soap.
Do this before you read on. An entry only works when you have just smelled the thing.
Clean, slightly alkaline, with a fatty note underneath and a layer of fragrance on top.
That fatty layer is the true nature of soap — it is made from fats and alkali. Everything else is added.
Unscented soap has almost only the fatty and alkaline layer, and it shows clearly the base of this whole group of products.
How to smell it
Smell the dry bar, then wet one corner and smell again — water releases the fragrance much more strongly. If you have unscented soap, compare them to separate the base from what is added.
Why this one is hard
Because “soapy” has become a word for a quality rather than an object. People say coriander smells soapy, and that is a roundabout association — in fact both contain straight-chain aldehydes.
Don’t confuse with
This entry
Bar soap
Household objects family
The saying that coriander smells of soap has a real basis: both contain straight-chain aldehydes.
Scientific note
Soap is a salt of fatty acids, made when alkali hydrolyses fats and oils. The base smell comes from residual fatty acids and from the reaction itself. Interestingly, the straight-chain aldehydes in some soap formulas belong to the same group as the compounds behind the smell of coriander leaf — the real chemical basis for saying coriander smells of soap.
In Vietnamese life
Bar soap was the main hygiene product in Vietnam before shower gel became common. Names such as Cô Ba soap and stone soap (xà bông đá) are instantly recognised by the older generation, and their smell goes with the well and the yard.